The present invention relates to apparatus for heating or cooling liquids. More particularly, it relates to apparatus for heating or cooling physiological fluids, such as whole blood and blood plasma, or liquids, such as dialysis fluid, which are used in the treatment of such physiological fluids. It also relates to containers in which or through which such fluids may be contained or circulated in order to effect heating or cooling.
It is frequently necessary or advisable during the course of medical treatment to heat or cool physiological fluids or to heat or cool liquids which are used in the treatment of such physiological fluids. For example, in haemodialysis it is common practice to heat the dialysis fluid before it enters the blood dialyzer. In heart/lung bypass surgery employing a blood oxygenator, blood which has been oxygenated outside the body is generally rewarmed to about body temperature before being returned to the patient. In the collection of whole blood from donors, it is sometimes desirable to cool the collected blood prior to further processing. Similarly, in plasmapheresis, where blood is taken from a donor and separated by centrifugation or membrane filtration into a fraction comprising cellular components and a fraction comprising plasma, it is desirable to have heating apparatus or cooling apparatus available prior to further handling of the separated fractions. As an example, if the cellular component fraction is to be returned to the patient, either as such or with a specified volume of replacement fluid added thereto, it would be advantageous to warm same to approximately body temperature prior to such return. On the other hand, apparatus for cooling may be needed if the separated plasma fraction is to be subjected to further processing such as filtration or treatment with an absorbent substance. It will also be recognized that in some circumstances heating or cooling may be needed on a batch basis. Batch heating, for example, may be used in connection with the transfusion of blood; in that case, a bag of blood which has been refrigerated is usually warmed before the patient is transfused. In other circumstances, it may be necessary or desirable to effect heating or cooling on a continuous basis. In blood dialysis, for example, it is customary to heat the dialysate prior to passing it through the dialyzer. In plasmapheresis procedures, it may be desirable to cool either the separated cellular fraction or the separated plasma fraction on a continuous basis.